1. Field of the Invention
This invention relates in general to the field of video processing. In particular, it pertains to the problem of recognizing points in video data at which ensuing images are unrelated to or markedly different from the preceding images. Such points are referred to as “scene changes.”
2. Description of Related Art
Scene change detection is the process of identifying points in a temporal sequence of images at which ensuing images are no longer related in content to the preceding images. Image sequences abound in the marketplace, especially in the form of digital video data, which occupies an important and growing share of the modern communications and information spectrum. The process of detecting scene transitions is useful for many applications, including but not limited to rapidly identifying new scenes in composite video sequences (for instance in the editing of TV news footage), capturing frames at the beginnings of new video scenes for indexing or cataloging purposes, and recognizing an intrusion into a monitored area via video capture for security reasons. Scene change detection also plays an essential role in many schemes for digital video compression, as detailed below.
Raw digital video data typically contains information about a sequence of images (herein referred to as frames) comprised of many pixels, with an encoded color value assigned to each pixel. For example, each frame may be a 720 by 480 array of pixels, with each pixel's color represented by three (red, green, blue) component values ranging from 0 to 255. As the raw data for each frame can be quite large, compression strategies seek to reduce the amount of data that must be stored or transmitted by taking advantage of redundancies of information inherent in video scenes. For instance, these strategies may exploit consistencies of color across regions in single frames, or they may take advantage of common shapes or colors that appear in several neighboring frames (as is typical within one scene of video data). In the latter strategy of exploiting temporal redundancy, after full data for an initial frame is recorded, data for ensuing frames may consist of various measurements of deviation from the initial frame rather than raw color data for every pixel. Such strategies are well known to allow extensive data compression and thus to permit transmission of video data at lower bit rates and to require less storage capacity for video files.